1. Field of the Invention
The present invention relates to a transfer and conveying apparatus for use in an image-forming machine for making an electrostatic latent image on a photoreceptor into a sensible image by using toner, and transferring the toner image onto a recording paper, and more particularly to a transfer and conveying apparatus designed to transfer the toner image onto a recording paper which is placed between a conveying belt trained about a pair of conductive rollers and the photoreceptor.
A typical prior art apparatus is shown in FIG. 1. The surface of a photoreceptor 1 is charged by a corona discharger 2, and light 4 is emitted in an exposure region 3, so that an electrostatic latent image corresponding to the information to be recorded is formed. This electrostatic latent image is made into a sensible toner image by a magnetic brush developing device 5. The toner image is then transferred onto a recording paper 9 which is conveyed in a direction indicated by an arrow 8 to a transfer region 7 provided with a corona discharger 6 for transferring the image. After such image transfer has taken place, the recording paper 9 is conveyed in the direction of arrow 11 by a belt conveyor 10 into a fixing apparatus.
In such prior art apparatus, since the toner image is transferred and fixed on the top surface of the recording paper 9, when different pieces of information are recorded on plural recording papers which are to be stacked, the first recording paper is positioned at the bottom of the stack with its recording side up, and the final recording paper is positioned at the top of the stack with its recording side up. In order to attain the papers in their original order, the sequence of the recording papers must be reversed. This procedure is very inconvenient.
Other prior art apparatus have been proposed to solve this problem. For example, one such prior art apparatus operates such that the recording paper is placed between a transfer and conveying belt which is trained about a pair of conductive rollers and a photoreceptor disposed beneath the transfer and conveying belt, and a toner image is transferred from the photoreceptor onto the recording paper and then conveyed away. In such prior art, the recording papers are piled up with the recording side down, such that when the entire pile of the recording papers is turned upside down, the recording papers are sequentially arranged from top to bottom.
In the prior art apparatus using such transfer and conveying belt, it is necessary to apply a high voltage through a brush to a pair of conductive rollers which support the transfer and conveying belt. This causes sparks to form, thereby making it difficult to perform the transfer and conveying operation in a stable manner.
In other prior art transfer and conveying apparatus, meanwhile, the toner is easily deposited on the outer circumference of the belt, such that the surface of the side opposite the recorded side of the recording paper becomes stained.
In still another prior art apparatus, such as that shown in FIG. 2, a right cylindrical photoreceptor 21 is charged by a corona discharger 22 and is exposed in an exposure region 23, and an electrostatis latent image is made into a sensible toner image by a magnetic brush developing device 24. The toner image on the photoreceptor 21 is transferred onto a recording paper 6 and conveyed in the direction of arrow 25 while being held against an endless belt 27. The belt 27 is trained about a pair of conductive rollers 28, 29 and one of the conductive rollers (28) is provided with a voltage from a DC power supply 31 by means of a brush 30. The axis of rotation 33 of the roller 28 is positioned directly above the axis of rotation 32 of the photoreceptor 21. With this arrangement, the recording paper 26 is held between the photoreceptor 21 and belt 27, so as to transfer the image, only in the vicinity of a line 34 which runs between the axis 32 and 33.
In this prior art apparatus, when the recording paper 26 is insufficiently attracted to the belt 27 after transfer of the image, the recording paper 26 sags as indicated by reference number 26a, and cannot be reliably conveyed. This results in jamming of the paper in the apparatus.